Multiple break gas blast circuit breaker



H. THOMMEN lJuly 2s, 1942.

MULTIPLE BREAK GAS BLAST CIRCUIT .BREKER' Filed March 25, 1941 L Mm z .m s .9 www F :la

Patented July. 28, 1942 UNITED 'STATES PATENT OFFICE MULTIPLE BREAK GAS BLAST CIRCUIT 11ans Thommen, Baden, S

Aktiengesellschaft Brown,

wtzerland, assignor to Boveri & Cie, Baden,

Y Switzerland, a joint-stock company 11 Claimst (CL 20G-148) This invention relates to circuit breakers and more particularly to multiple break gas blast circuit breakers.

There is a non-uniform voltage distribution along the several current interrupting points of a multiplie break circuit breaker of the type having a plurality of arcing contacts electrically and spatially in series. This uneven voltage distribution is particularly disadvantageous in circuit breakers in which the arcing contacts are subjected to a blast of gas under pressure to extinguish the arcs, since it results in a decrease in the rupturing capacity of the circuit breaker and an increase in the consumption of the arc-extinguishing medium.

1n order to overcome this disadvantage it has already been proposed in gas blast circuit breakers with multiple interruption for interrupting the power and a voltage isolating switch in series with the former, to .bridge over all the points of current interruption of the power circuit breaker by means of current-reducing damping devices, so that when the power circuit breaker is opened the resulting residual current can be linterrupted by the voltage isolating switch.

The object of the present invention is to obtain a still better lcontrol of the voltage over the individual points of current interruption in gas blast circuit breakers than has hitherto been possib-1e with the arrangements used up to the present. According to the invention this is achieved by bridging ov'er only the outer points of current interruption by impedances which are so dimensioned that the voltage to be interrupted distributes itself uniformly over the individual arcing contacts and enables the arc to be extinguished quite safely. Thus only those points of interruption which have to deal with the greater part of the voltage when the circuit is being broken are bridged over by a condenser or resistor. Furthermore, the parallel connected impedances can be made comparatively small because they are only stressed during short periods of time. The residual current which results upon an opening of the circuit breaker is interrupted quite easily by the remaining arcing contacts which are not bridged over by impedances.

The objects and advantages of the invention will be apparent from the following specidcation when taken with the accompanying drawing in which: y

Fig. 1 is a somewhat diagrammatic side elevation, with parts in central section, of an ernbodiment of the invention;

Fig. 2 is a side elevation, with parts in section, 55 ing manner.

of multiple break gas blast circuit breaker with external resistive impedances shunted across two sets of arcing contacts at each end of the circuit breaker.

Fig. 3 is a side elevation, on a smaller scale, of a circuit breaker in which capacitive impedances are employed; and

Fig. Li is a central vertical section of the lower part of a modied circuit breaker construction in which the damping resistance is a semi-conductive layer on the wall of the chamber.

As shown in Fig. l, the multiple break gas blast circuit breaker comprises a plurality of vertically arranged arc extinguishing chambers, identied generally by the reference numerals la to Ih, respectively, that each house a pair of cooperating contacts. Hollow insulators 2 iorm the outer walls of the several arc extinguishing chambers, and metal plates or castings 3 are arranged between adjacent pairs of insulators, and upon the upper insulator ih to v form the transverse walls of the compartments. The electrical conductors or lines L, L' are connected to a terminal t on the cap member 5 which is supported by the top plate 3, and to the base casting E that forms the bottom wall of the lower chamber la. The base t is mounted upon a hollow insulator column, not shown, through which a pressure gas is supplied to the arcing chambers to separate the cooperating contacts and to extinguish the resulting arcs.' Openings l extend through the base i5 to admit the pressure gas to the bottom compartment, and ports in the several transverse wall plates 3 permit the flow of pressure gas from one chamber to the next.

Each transverse wall plate has a passage 'Si that extends laterally from the edge of the plate to the central portion where it terminates in a downwardly opening nozzle contact l). A pin contact ii cooperates with each nozzle contact, the pin contacts being slidably supported in cylinders i2 that extend upwardly from the base l5 and from each plate 3 except that plate which forms the top wall of the `upper chamber lh. Springs it normally retain the pin contacts il in engagement with the cooperating nozzle contacts it, and the pin contacts are so shaped that they are forced downwardly when a pressure gas is admitted to the arcing chambers. The several sets of arcing contacts lll, Il are thus arranged electrically and spatially in series between the line conductors L, L.

The construction as so far described has been previously proposed, and operates in the follow- Pressure gas is admitted to the arcing chambers through the openings 'I of the base plate 6 upon the manual or automatic actuation of valve mechanism, not shown. The pressure gas forces the pin contacts I I downwardly against the force exerted by the springs I2, and the pressure gas then flows over the ends of the pin contacts and to atmosphere through the nozzle contacts III as arc extinguishing blasts.

In accordance with this invention, the voltage to be interrupted is distributed uniformly over the several sets of arcing contacts by connecting current damping impedances in parallel with only one or more of the current interrupting points at each end of the circuit breaker. As illustrated diagrammatically in Fig. 1, these damping impedances are resistances |3a, I3b, I3g, I3h that are shunted across the sets of arcing contacts within the-two end chambers at each end of the circuit breaker. The resistances may be, and preferably are, graded, i. e., the resistances I3a and I3h are of greater magnitude than the resistances I3b and I3g. Upon the opening of the circuit breaker contacts, a predeterminedvoltage distribution is established across the more heavily stressed end points of current interruption by the shunt resistances, and the residual current that tends to flow through the shunt resistances is then interrupted by the intermediate sets of arcing contacts.

It is to be understood that the usual disconnect switch for voltage isolation will be arranged in series with the multiple break circuit breaker, but the disconnect switch is not relied upon to interrupt the flow of a residual current.

In a practical form of the invention, as shown in Fig. 2, the series of insulators 2 and transverse wall plates 3 are retained in vertically assembled relation by insulating rods or tubes I4 that extend between flanges I5 of the base plate 6 and the metal cap member 5'. Cylindrical layers or tubes Isa, IBb, I6g, I6h of resistance or semiconductive material are provided upon one or, as shown, upon both of the supporting rods I4, and are connected across the arcing contacts of the two outer sets of arcing contacts at each end of the circuit breaker.

A capacitive type of voltage distributing impedance, as shown in Fig. 3, comprises approximately conical metal plates I1, I8 that are secured to and in electrical contact with the base plate 6a and the outer cap 5a of a vertically arranged series of gas blast arcing contacts, not shown, within the arc extinguishing chambers formed by the insulators 2 and transverse wall plates 3. The opposed rims II, I 8 oi' plates I1, I8 are rounded to prevent corona discharge, and the plates are covered with an insulating material I9 to prevent ashover when the circuit breaker is opened.

It is sufficient, in some instances, to shunt only one set oi arcing contacts, at each end of the series. with a current damping impedance. As shown in Fig. 4, layers I3 of a semi-conductive or resistance material are applied to or formed on the walls of the insulator 2 of the arc extinguishing chamber la. The insulator 2 of the next adjacent arc extinguishing chamber Ib is not provided with the semi-conductive layers. The arc extinguishing chamber Ih at the top of the column will be provided with a shunt impedanoe, preferably in the form oi a semi-conductive layer or layers I3 on the associated insulator 2, but all intermediate arcing chambers will not be shunted by current damping resistances in this embodiment of the invention.

In addition to the embodiments herein shown and described there are also further possibilities as regards the manner in which the parallel-connected resistors and capacities can be arranged on the circuit breaker. For instance, the insulators 2 oi' the are extinguishing chambers may be made of a high ohmic resistance material. When condensers are employed to bridge over the outer points of interruption, those parts oi the extinguishing chambers which surround the arcing contacts of these switch points can be used as condenser elements or the walls of the extinguishing chambers can be constructed from a material having a high dielectric constant so that the extinguishing chambers themselves then act as condensers. In all these cases, it is preferable that the metallic surfaces o1' the individual switch elements be made as small as possible so that the resistors or condensers can also be kept small and as simple as possible.

Gas blast circuit breakers with multiple interruption and voltage regulation as described above in accordance with the invention can be connected in series with a simple air isolating switch, the latter being opened and closed after the circuit has been interrupted by the power circuit breaker. It is also possible to subdivide the arcing contacts for the multiple break by arranging them on two supporting insulators or columns, the power switching points being in series with the isolating switch. The end points of interruption on each column are then bridged-over by impedances in order to obtain the desired voltage distribution over the series-connected switch points of the gas blast circuit breaker.

I claim:

1. In a multiple break gas blast circuit breaker, a plurality of sets of cooperating arcing contacts arranged electrically and spatially in series, and current damping impedances connected across only the outer sets of cooperating arcing contacts at each end of the series, whereby the residual current through said impedance is interrupted by an intermediate set of cooperating contacts that is not shunted by a current damping impedance.

2. In a multiple break gas blast circuit breaker, a vertically arranged column of arc extinguishing chambers, each chamber comprising a hollow insulator and transverse walls carrying respectively a nozzle contact and a cooperating pin contact, and means for establishing a predetermined voltage distribution along said sets of c0- operating contacts, said means comprising current damping impedances shunted across only the outer sets of said cooperating contacts, whereby the residual current flow through said impedances is interrupted by the intermediate sets of cooperating contacts that are not shunted by impedances.

3. In a gas blast circuit breaker, a series of vertically arranged arc extinguishing chambers each housing a set of nozzle and cooperating pin contacts, one of said contacts being movable upon the introduction of a pressure gas into the chamber to separate the contacts, and current damping impedances shunted across only the sets of cooperating contacts of the two end arc extinguishing chambers at each end of said series, the intermediate sets of cooperating contacts serving to interrupt the residual current ow through said impedances.

4. In a gas blast circuit breaker, the invention as claimed in claim 3, wherein the impedances shunted across the end sets of cooperating contacts are of g-reater magnitude than the impedances shunted across the adjacent sets of cooperating contacts.

5. In a gas blast circuit breaker, a series of vertically arranged arc extinguishing chambers each housing a set of nozzle and cooperating pin contacts, one of said contacts being movable upon the introduction of a pressure gas into the chamber to separate the contacts, and current damping impedances shunted across only the sets of lcooperating contacts of the end arc extinof said insulating members and shunted across the outer sets of cooperating contacts.

'7. The invention as claimed in claim 6, wherein said impedances comprise layersof semi-conductive material.

8. In a multiple break gas blast circuit breaker, a series of vertically arranged arc extinguishing chambers each comprising a cylindrical insulator and transverse metallic walls and each housing a cooperating set of gas blast arcing contacts, conductive members at the opposite ends' of said series of chambers, and capacitive impedances in shunt with the cooperating contacts of the outer arc extinguishing chambers, said impedances comprising a metal plate secured to each of said conductive members and extending about and in spaced relation to the outer arc extinguishing chambers and cooperating with a transverse metallic wall of said outer chambers to form a capacitative impedance.

9. The invention as claimed in claim 8, wherein said conductive members are coated with insulating material.

10. In amultiple break gas blast circuit breaker, a series of alined arc extinguishing chambers each comprising a cylindrical Wall and transverse metallic walls, and cooperating gas blast contacts carried by the transverse walls of .eachchamben the outer walls of the interme.

diate chambers consisting of 'insulating material, and the cylindrical walls of the end chambers of the series including semi-conductive material in parallel with the associated sets of gas blast contacts.

11. The invention as claimed in claim 10, wherein the cylindrical walls of all of said chambers comprise hollow insulators, and said semii conductive material comprises a layer of semi` conductive material upon the hollow insulators of the end chambers.

HANS THOMMEN. 

